Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

3. Amino Acids

Amino Acid Groups

Biochemistry

3. Amino Acids

Amino Acid Groups

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Multiple Choice

Which of the following amino acids contains a positively charged (basic) side chain at physiological pH?

Serine

Leucine

Lysine

Aspartic acid

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Understand the concept of physiological pH: Physiological pH is typically around 7.4, which is slightly basic. At this pH, amino acids can exist in their ionized forms depending on the properties of their side chains.

Classify the amino acids based on their side chain properties: Amino acids can have acidic, basic, polar, or nonpolar side chains. Basic side chains are positively charged at physiological pH, while acidic side chains are negatively charged.

Analyze the side chains of the given amino acids: Serine has a polar hydroxyl group, Leucine has a nonpolar aliphatic side chain, Lysine has a basic side chain with an amino group, and Aspartic acid has an acidic carboxyl group.

Determine the charge of the side chains at physiological pH: At pH 7.4, Lysine's amino group is protonated, making it positively charged. Aspartic acid's carboxyl group is deprotonated, making it negatively charged. Serine and Leucine do not have charged side chains at this pH.

Conclude that Lysine is the amino acid with a positively charged (basic) side chain at physiological pH, based on its chemical structure and ionization behavior.